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Visibility of matter

  1. Feb 15, 2010 #1
    If over 99.9% of an atom's mass is concentrated in the nucleus, the rest being "empty", why is matter (simply composed of atoms) clearly visible, rather than being largely invisible?

    Also, why can't I move my hand through a solid table? Where is this empty space constituting the majority of the table?

    Might be a silly question, but it's just a random thought that struck me :smile:
  2. jcsd
  3. Feb 15, 2010 #2


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    We see via photons. Photons interact with the electron shell, not with the nucleus.

    Same thing. We physically interact with the electron shells, not with the nucleus.

    Answer this question: why can I not push a 2x4 through a basketball, even though the basketball is mostly empty space?
  4. Feb 15, 2010 #3
    Like forces repel each other! Nothing ever touches, it only comes close to touching!
  5. Feb 15, 2010 #4
    Can you explain physically why this is? Isn't the shell just composed of electrons orbiting the nucleus, rather than being an impenetrable solid?

    As above
  6. Feb 15, 2010 #5

    Doug Huffman

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    The orbit analogy is inept and obsolete.
  7. Feb 15, 2010 #6


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    The electrons form an orbital - a cloud; this is not the same as an orbit. An orbital is simply a function that defines the probability of finding an elelctron in a certain place if we go to look for it. It says absolutely nothing about what the electron is doing when we are not looking for it.

    While not really imprenetrable, the electrons are what the photons interact with. it is also what the electron orbitals in the atoms of your hand interact with when you try to touch something.
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